Neutralization principles for the extraction and transport of ion beams

Abstract

The strict application of conventional extraction techniques of ion beams from a plasma source is characterized by a natural intensity limit determined by space charge.The extracted current may be enhanced far beyond this limit by neutralizing the space charge of the extracted ions in the first extraction gap of the source with electrons injected from the opposite side. The transverse and longitudinal emittances of a neutralized ion beam, hence its brightness, are preserved. Results of beam compensation experiments, which have been carried out with a laser ion source, are resumed for proposing a general scheme of neutralizing ion sources and their adjacent low-energy beam transport channels with electron beams. Many technical applications of high-mass ion beam neutralization technology may be identified: the enhancement of ion source output for injection into high-intensity, low-and high-energy accelerators, or ion thrusters in space technology, for the neutral beams needed for plasma heating of magnetic confinement fusion devices, and for future accelerator-driven systems for fusion, fission and nuclear waste incineration. The strict application of conventional extraction techniques of ion beams from a plasma source is characterized by a natural intensity limit determined by space charge. The extracted current may be enhanced far beyond this limit by neutralizing the space charge of the extracted ions in the first extraction gap of the source with electrons injected from the opposite side. The transverse and longitudinal emittances of a neutralized ion beam, hence its brightness, are preserved. Results of beam compensation experiments, which have been carried out with a laser ion source, are resumed for proposing a general scheme of neutralizing ion sources and their adjacent low-energy beam transport channels with electron beams. Many technical applications of high-mass ion beam neutralization technology may be identified: the enhancement of ion source output for injection into high-intensity, low-and high-energy accelerators, for ion thrusters in space technology, for the neutral beams needed for plasma heating of magnetic confinement fusion devices, and for future accelerator-driven systems for fusion, fission and nuclear waste incineration. CERN LHC/2000-5

Effect of Solenoidal Magnetic Field on Time Evolution of Ion Beam Emittance in Laser Ion Source

“…To investigate the effect of the variation in the ion current density on the plasma meniscus, the ion current densities at the ion extraction point were compared to the spacecharge-limited current density calculated using the Child-Langmuir law. Laser ablation plasmas have a drift veloc- ity; therefore, the space-charge-limited current density was calculated using the following equation [11]:…”

Plasma shape control by pulsed solenoid on laser ion source

“…The boundary shape between plasma and an ion beam is determined by a relationship of plasma density and the space charge limit current density described as Child-Langmuir equation. The equation is described as [9]…”

Maximizing ion current by space-charge neutralization using negative ions and dust particles

“…5 Similar techniques are routinely used for beam charge compensation in numerous technical fields. 6 For example, in ion thrusters for spacecraft propulsion, 7 the ejected ion beams are charge and current neutralized with electrons supplied by hollow plasma cathodes. We note, however, that the beam extraction stage of an ion thruster is not neutralized, and, therefore, the beam current is space charge limited.…”